脉冲电解法预处理酸性染料废水

研究了脉冲电解法预处理酸性偶氮类染料废水的处理效果,考察了不同工艺条件对废水COD去除率、脱色率和可生化性的影响。结果表明,脉冲电源峰值电压12 V,频率600 Hz,占空比50%的条件下电解40 min后,COD去除率可达59%,废水脱色率达91.4%,BOD5/COD由0.09提高至0.34。在相同条件下,脉冲电解法的电流效率是直流电解法的2倍左右。与现行常用的铁/碳反应床相比,脉冲电解法在成本上也具有一定的优势,应用前景较好。     

吸附增效低温等离子体法去除甲苯废气的研究

采用150Hz中频高压交流电源作为低温等离子体发生源,选用典型的微孔γ-Al2O3球形颗粒吸附剂(以下简称γ-Al2O3)作为等离子体反应器填充材料,协同低温等离子体法催化降解甲苯废气。考察了在不同条件下,γ-Al2O3的甲苯吸脱附效果和吸附增效低温等离子体法的甲苯去除效果。结果表明,甲苯降解反应主要发生在γ-Al2O3的表面,甲苯的去除率在一定的浓度范围内与γ-Al2O3表面吸附的甲苯量成正比关系;填充γ-Al2O3有利于提高甲苯去除率及等离子体反应器能量利用率;γ-Al2O3对臭氧的降解表现出一定的促进作用。     

黄河下游历史泥沙灾害的宏观特征及其与流域因素和人类活动的关系（Ⅱ）：—人类活动、历史地震及地形因子的影响

以历史上黄河下游的决溢频率为泥沙灾害的代用指标，研究了人类活动，历史地震及地形因子对黄河下游历史泥沙灾害的影响，研究表最，人类活动是影响黄河下游泥沙灾害的重要因素，历史上人口的增加使下游决溢频率增大，人口低谷与决溢频率的低值时段相应，历史上农牧交错带的南移与下游决溢频率的减小相伴发生。北移则导致决溢频率的增大，历史地震对黄河下游历史泥沙灾害有一定的影响，黄河下游历史泥沙灾害表现出明显的空间分异，这种分异与平原地貌条件的沿程变化有密切的关系。     

Influence of GSTM1 and GSTT1 genotypes and confounding factors on the frequency of sister chromatid exchange and micronucleus among road construction workers

In the present study, we have investigated the influence of polymorphism of GSTM1 and GSTT1 genes and confounding factors such as age, sex, exposure duration and consumption habits on cytogenetic biomarkers. Frequency of sister chromatid exchanges (SCEs), high frequency cell (HFC) and cytokinesis blocked micronuclei (CBMN) were evaluated in peripheral blood lymphocytes of 115 occupationally exposed road construction workers and 105 unexposed individuals. The distribution of null and positive genotypes of glutathione-S transferase gene was evaluated by multiplex PCR among control and exposed subjects. An increased frequency of CBMN (7.03 ± 2.08); SCE (6.95 ± 1.76) and HFC (6.28 ± 1.69) were found in exposed subjects when compared to referent (CBMN - 3.35 ± 1.10; SCE - 4.13 ± 1.30 and HFC - 3.98 ± 1.56). These results were found statistically significant at p < 0.05. When the effect of confounding factors on the frequency of studied biomarkers was evaluated, a strong positive interaction was found. The individuals having GSTM1 and GSTT1 null genotypes had higher frequency of CBMN, SCE and HFC. The association between GSTM1 and GSTT1 genotypes and studied biomarkers was found statistically significant at p < 0.05. Our findings suggest that individuals having null type of GST are more susceptible to cytogenetic damage by occupational exposure regardless of confounding factors. There is a significant effect of polymorphism of these genes on cytogenetic biomarkers which are considered as early effects of genotoxic carcinogens.     

KALMAN FILTER CALCULATION OF SAMPLING FREQUENCY WHEN DETERMINING ANNUAL MEAN SOLUTE CONCENTRATIONS

ABSTRACT: A linear filter (Kalman filter) technique was used with a Streamflow-concentration model the minimize surface water quality sampling frequencies when determining annual mean solute concentrations with a predetermined allowable error. The Kalman filter technique used the stream discharge interval as a replacement for the more commonly used time interval. Using filter computations, the measurement error variance was minimized within the sample size constraints. The Kalman filter application proposed here is applicable only under several conditions including: monitoring is solely to estimate annual mean concentration; discharge measurement errors are negligible; the Streamflow-concentration model is valid; and monthly samples reflect the total variance of the solute in question.     

INSTANTANEOUS PEAK FLOW ESTIMATION PROCEDURES FOR NEWFOUNDLAND STREAMS1

ABSTRACT: A procedure of estimating instantaneous flood flows for various return periods on the Island of Newfoundland is presented. The procedure is based on annual maximum instantaneous flows rather than annual maximum daily-mean flows, as the latter requires the conversion of estimated daily-mean flows into instantaneous flows. Regression equations were developed for each of three homogeneous regions for the desired return periods. The flood flow estimation capability of the presented procedure is demonstrated to be better than any other currently available procedure on the Island.     

REGIONAL FLOOD EQUATIONS FOR THE PROVINCES OF ONTARIO AND QUEBEC1

ABSTRACT: When nonparametric frequency analysis was performed on 183 stations from Ontario and Quebec, unimodal and multimodal maximum annual flood density functions were discovered. In order to determine generating mechanisms, a monthly partitioning of the annual maximum floods was undertaken. The timing of the floods revealed that the unimodal distributions reflected a single flood generating mechanism while the multi-modal densities reflected two or more mechanisms. Based on the division of the flood series by mechanisms, nine homogeneous regions were delineated. L-moment distributional homogeneity tests along with smaller standard errors for the regional equations supported the delineation.     

JUSTIFICATION FOR A REDUCTION IN THE CREST-STAGE GAGE PROGRAM IN LOUISIANA1

The crest-stage gage program in Louisiana was evaluated to determine if the data were adequate for use in developing regional flood-frequency equations and to determine if any crest-stage gage stations could be discontinued. An abundance of data at many crest-stage gage stations and a lack of data for urban areas and flat-slope areas indicated a need for a shift in the number, type, and locations of gages. Correlations and comparisons of annual peak discharges and watershed characteristics of 96 existing stations resulted in the elimination of 72 stations and the addition of one new station, reducing the total network to 25 stations that could be used for future flood-frequency analyses. The adequacy of the reduced network for development and verification of regional flood-frequency equations was tested by comparing a set of regional flood-frequency equations developed using data from the full network with a set developed using data from the reduced network. The results indicate that the crest-stage gage network can be reduced to 25 stations and still provide adequate information for future flood-frequency analyses.     

SOME GEOMORPHIC RELATIONSHIPS AND HYDROGRAPH ANALYSIS1

ABSTRACT: First order drainage channels originate when the tractive force exerted by flowing water is sufficient to move surface sediment. The amount of runoff available to move sediment is a function of geologic and climatic characteristics. An experimental analysis showed that soils derived from fine grained rocks had lower infiltration rates and higher runoff volume than soils derived from coarser grained rocks in a semi-arid climate. Root density and penetration increased in a more humid climate and increased infiltration rates. The number of first order channels was inversely proportional to the infiltration capacity of the soil. Each first order channel acts as a source area for surface runoff. The distribution of first order channel distances from the gage determines the timing of the delivery of water to the gage. A comparison of the frequency histogram of first order channel distances for drainage basins in Pennsylvania and their hydxographs of runoff from general storms showed marked similarity. This close correspondence indicated the shape of the surface runoff hydrograph and was largely controlled by the distribution of first order channel distances.     

CAUSES OF PEAK FLOWS IN NORTHWESTERN MONTANA AND NORTHEASTERN IDAHO1

ABSTRACT: Both catchment experiments and a review of hydrologic processes suggest a varying effect of forest harvest on the magnitude of peak flows according to the cause of those peak flows. In northwestern Montana and Northeastern Idaho, annual maximum flows can result from spring snowmelt, rain, mid-winter rain-on-snow, or rain-on-spring-snowmelt. Meteorologic and physical data were used to determine the cause of annual maximum flows in six basins which had the necessary data and were smaller than 150 mi². Rain-on-spring-snowmelt was the most frequent cause of annual maximum flows in all six basins, although there was a strong gradient in the magnitude and cause of peak flows from southwest to northeast. Less frequent mid-winter rain-on-snow events caused the largest flows on record in four basins. Mid-winter rain-on-snow should be distinguished from rain-on-spring-snowmelt because of differences in seasonal timing, the relative contributions of rain vs. snowmelt, and the projected effects of forest harvest. The effects of mixed flood populations on the flood-frequency curve varied from basin to basin. Annual maximum daily flows could not be reliably predicted from rainfall and snowmelt data.